Vehicle engines produce oxides of nitrogen (NOx) as a component of vehicle emissions. In particular, lean-burn gasoline and diesel engines tend to produce higher levels of NOx than conventional gasoline engines.
In an effort to reduce NOx levels in vehicle emissions, manufacturers employ emissions control systems with engine sensors and NOx storage catalysts. The NOx storage catalysts absorb and decompose the NOx with combustible gases such as carbon monoxide (CO) or hydrocarbon (HC). While reducing NOx levels, these systems tend to increase the level of hydrocarbons in vehicle emissions.
Recent designs in NOx sensors allow improved reduction of NOx emissions. NOx sensors may be integrated in the NOx storage catalyst. The NOx sensor detects NOx concentrations in emissions. The sensor communicates with an engine control system and provides data regarding NOx levels. The engine control system takes actions to reduce the NOx levels.